A standard barrel of crude oil contains 42 gallons or approximately 159 liters. This measure has been used since the late 19th century when the oil industry was in its infancy. Interestingly, the size of a barrel was not standardized until the early 20th century, leading to some variations in the past.

Crude oil is a complex mixture of hydrocarbons, with varying characteristics depending on its source. The composition of crude oil includes different types of hydrocarbons like paraffins, aromatics, and naphthenes, with varying densities and viscosities. It also contains impurities like sulfur, nitrogen, and metals.

There are different types of crude oil, often classified by their location of origin. For example, West Texas Intermediate (WTI) and Brent crude are well-known varieties. The quality of crude oil, as well as its sulfur content, plays a significant role in determining its market value.

Crude oil is extracted from underground reservoirs, typically located beneath land or offshore. Once extracted, it undergoes refining processes at oil refineries. These processes separate crude oil into various components like gasoline, diesel, jet fuel, and other petroleum products. Each of these components has different applications in our daily lives.